CN103956949B - Three grades of formulas rise/and the permanent slip of generator two-phase excitation exchanges startup model and control method - Google Patents

Abstract

The present invention relates to a kind of three grades of formulas to rise/the permanent slip of generator two-phase excitation exchanges the Controlling model and control method that start, the technical scheme adopted is: and three grades of formulas rise/and generator excitation machine stator adopts two symmetrical excitation winding, during electric motor starting, exciter stator passes into the two-phase alternating current of phase place mutual deviation 90 °, respond to magnetic potential frequency by regulating the additional ac frequency of exciter stator and rotor and keep permanent slip, thus ensure that the three-phase alternating current amplitude that exciter exports reaches stable, and then provide enough stable exciting currents for the starting of main generator.And then provide enough stable exciting currents for the starting of main generator, can ensure three grades of formulas rise/generator realizes steadily, reliably starting.

Description

Three-stage starter/generator two-phase excitation constant slip AC starting model and control method

technical field

The invention belongs to the technical field of three-stage generator/generator AC start control, and in particular relates to a control model and control method for three-stage generator/generator two-phase excitation constant-slip AC start.

Background technique

At present, three-stage brushless generators are widely used in the fields of aviation AC power systems, electric vehicles and wind power generation systems. This type of motor is used as a generator with mature technology, but this type of motor has no self-starting capability and requires a special starter motor to It starts, which complicates its starting. If the original three-stage brushless generator can be improved and controlled to make it work in the electric state, that is, to realize the integration of starting and power generation, the corresponding starting supporting equipment can be saved, thereby reducing the volume and weight of the system.

The three-stage generator/generator is mainly composed of a main generator, an exciter, an auxiliary exciter (permanent magnet machine) and a rotating rectifier. In the static starting stage of the motor, if a direct current is applied to the stator winding of the exciter, no induced potential will be generated on the rotor winding of the exciter, and there will be no excitation current in the rotor winding of the main generator, and the main generator will not be able to run electrically. Therefore, the key to realizing the three-stage starter/generator startup is to solve the excitation problem during startup.

In order to solve the excitation problem of the three-stage generator/generator, relevant scholars at home and abroad have proposed single-phase AC excitation and three-phase AC excitation schemes. The single-phase AC excitation is limited by the capacity of the exciter body and the amplitude of the power supply voltage. Not high, the energy transmission of the stator and rotor is poor. For three-phase AC excitation, the structural design of the motor body needs to be greatly changed, the utilization rate of the windings is poor, and the switching mode of AC and DC excitation is complicated.

On the basis of the above-mentioned related research, the Chinese patent CN103457427A, titled "an exciter structure and control method for a three-stage starting/generating system", CN103532454A, titled "two-phase brushless exciter in a three-stage Control method during start-up and power generation of a starter/generator system”, which discloses a new excitation structure and method that does not need to greatly change the structure of the motor and can improve the utilization rate of the excitation winding, that is, the excitation winding is a two-phase symmetrical winding. Two-phase excitation mode, when the motor is in the starting state, the exciter uses two-phase alternating current with a difference of 90° for excitation; when the motor is in the generating state, the two-phase excitation windings are connected in reverse series and connected to direct current for excitation.

The excitation mode described in CN103532454A only describes the way in which the two-phase excitation winding is connected to the two-phase alternating current in the starting state of the three-stage generator/generator, and does not propose a specific control method, nor does it explain the control characteristics of the excitation current. This makes it difficult to implement the two-phase AC excitation method.

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a control model and control method for a three-stage generator/generator two-phase excitation constant-slip AC start to realize a three-stage generator/generator using a two-phase excitation structure Stable control of the excitation current when the motor starts.

Technical solutions

A three-stage starter/generator two-phase excitation constant-slip AC start control model is characterized in that the three-stage starter/generator two-phase exciter control model is:

Among them: U _a , U _b , U _c are the rotor phase a, b, c winding voltages respectively, θ is the excitation angular velocity, θ _r is the rotor angular velocity, K _r is the voltage conversion coefficient, is the impedance angle of the stator winding;

The θ=ω ₁ t, ω ₁ is the angular frequency of the excitation voltage, and t is the running time of the exciter;

The θ _r = ω _r t, ω _r is the electrical angular velocity of the rotor;

said R _s is the internal resistance of the stator winding, L _m is the mutual inductance of the stator and rotor windings, L _s is the self-inductance of the stator winding, and U _m is the maximum value of the excitation voltage;

said

A control method for realizing a three-stage starter/generator two-phase excitation constant-slip AC start using the control model, characterized in that the steps are as follows:

Step 1: Feed the stator of the two-phase exciter into a two-phase symmetrical alternating current with an initial excitation voltage frequency of f ₁ and a maximum alternating voltage amplitude of U _m , where the initial f ₁ is the slip reference (f ₁ -f _r ) ^* , and 4Hz≤f ₁ ≤10Hz;

Step 2: The speed n of the main generator is obtained by the position sensor of the main generator. The main generator and the exciter are installed coaxially, so the frequency of the magnetic force induced by the rotor of the exciter is f _r = p n/60, and p is the main generator Number of pole pairs;

Step 3: Subtract the difference between f ₁ and f _r , and compare the obtained difference f ₁ -f _r as the feedback value with the slip reference (f ₁ -f _r ) ^* , and obtain a new excitation through PI operation Machine excitation voltage frequency f ₁ ';

Step 4: Feed the two-phase exciter stator into two-phase symmetrical alternating current with excitation voltage frequency f ₁ ' and maximum alternating voltage amplitude U _m , repeat steps 2 to 4, and control when the speed of the main generator rises to the rated speed Finish.

Beneficial effect

The present invention proposes a three-stage generator/generator two-phase excitation constant-slip AC starting control model and control method. The technical solution adopted is: the stator of the three-stage generator/generator exciter adopts two-phase symmetrical excitation windings When the motor is started, the exciter stator is fed with two-phase alternating current with a phase difference of 90°. By adjusting the frequency of the applied alternating current to the exciter stator and the frequency of the induced magnetic force of the motor rotor, a constant slip is maintained, so as to ensure the amplitude of the three-phase alternating current output by the exciter. To achieve stability, and then provide enough stable excitation current for the start of the main generator. Furthermore, sufficient and stable excitation current is provided for the starting of the main generator, which can ensure the stable and reliable starting of the three-stage generator/generator.

Compared with prior art, the beneficial effect of this method is:

(1) Compared with single-phase AC excitation, this control method has high excitation efficiency when the motor is started, and the induced potential of the rotor of the exciter is not limited by the excitation voltage, so that it can meet the dual-function requirements of starting/generating for a large-power main generator;

(2) Compared with the three-phase AC excitation, the utilization rate of the two-phase excitation winding in this control method is high, and the switching operation with the DC excitation of the auxiliary exciter is simple when starting/generating conversion;

(3) In terms of the implementation of the control method, compared with the single-phase excitation method, the excitation power topology DC boost module can be omitted to reduce the volume and weight of the controller;

(4) This method can realize the stable control of the excitation current, which is beneficial to the reliable starting control of the main generator.

Description of drawings

Figure 1 is a two-phase excitation structure diagram of a three-stage generator/generator;

Figure 2 is the exciter stator impedance triangle;

Fig. 3 is a block diagram of a three-stage starter/generator two-phase excitation constant-slip AC starting control method;

Fig. 4 is a Matlab simulation model of a three-stage starter/generator two-phase excitation constant-slip AC starting control method;

Figure 5 is an external two-phase voltage waveform when a constant-slip three-stage generator/generator two-phase exciter starts;

Fig. 6 is a Matlab simulation output curve of a three-stage generator/generator two-phase excitation constant-slip AC starting control method.

detailed description

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

The invention proposes a three-stage generator/generator two-phase excitation constant-slip AC starting control method, which can ensure that the excitation current of the main generator remains stable during the starting process of the three-stage generator/generator.

The establishment process of the three-stage starter/generator two-phase excitation constant slip AC starting control model is as follows:

Step 1: Let the two-phase alternating current of the given exciter in Figure 1 be:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; t</span>}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, U _α and U _β are the excitation voltage of the stator two-phase winding; U _m is the maximum value of the excitation voltage.

Step 2: The two-phase AC excitation voltage is transformed into the dq0 rotating coordinate system after 2s/2r coordinate transformation. The formula is:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}& \mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}& \mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, u _ds , u _qs are the winding voltages of stator AC and direct axis respectively; θ=ω ₁ t is the excitation angular velocity.

After derivation, u _ds = U _m cos2θ, u _qs = -U _m cos2θ can be calculated.

Step 3: Bring the above results into the following two-phase exciter voltage equation:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; dr</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; qr</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cccc}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& {\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& {\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& {\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; dr</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; qr</span>}}\end{array}\right]<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; p</span>}\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; dr</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; qr</span>}}\end{array}\right]<span\; class="notranslate">\; +</span>\left[\begin{array}{c}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}\\ <span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; qr</span>}}\\ <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; dr</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, u _qr , u _dr are the rotor alternating and direct axis winding voltages respectively; R _s , R _r are the internal resistances of the stator and rotor windings respectively; ω ₁ is the excitation voltage angular frequency; ω _r is the rotor electrical angular velocity; p is the differential operator .

In the case of no-load of the main exciter rotor winding, the current of each phase is 0, that is, i _dr and i _qr are 0. Bringing into the voltage equation of formula (3), the differential items in formula (3) are all 0 in steady state, and we can get:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\\ <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; dr</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; qs</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; qr</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Among them, ψ _qr = L _m i _ds , ψ _dr = L _m i _qs are the rotor cross-axis and direct-axis flux linkage respectively, and L _m is the mutual inductance of the stator and rotor windings.

Step 4: The transformation formula from the synchronous rotating coordinate system to the three-phase stationary coordinate system is:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; dr</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; qr</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Among them, U _a , U _b , and U _c are the winding voltages of phase a, b, and c of rotors respectively; θ=ω ₁ t, θ _r =ω _r t.

Step 5: The expression of the three-phase output voltage of the two-phase exciter can be calculated from formulas (4) and (5):

in, is the impedance angle of the stator winding, as shown in the stator winding impedance triangle in Figure 2.

Equation (6) is the three-phase output voltage expression of the main exciter during AC excitation, and its output voltage amplitude is related to the two-phase excitation AC frequency ω ₁ , the motor speed θ _r and the maximum value U _m of the excitation voltage.

Due to the particularity of the application environment, the three-stage starter/generator is mostly started with load, which requires sufficient potential induced on the armature winding of the exciter to provide sufficient excitation current for the main generator, and according to (6 ) formula, it is easy to know that ω ₁ -ω _r has the greatest influence on the output voltage, and (ω ₁ -ω _r )/ω _r is the slip s of the asynchronous motor from the knowledge of electromechanics, and ω ₁ -ω _r is the stator external The angular frequency slip between the AC angular frequency and the induced magnetic potential of the motor rotor.

The step-type starter/generator two-phase excitation constant-slip AC starting control method is characterized in that it adjusts the slip between the frequency of the applied AC power to the stator of the exciter and the frequency of the induced magnetic force of the motor rotor to keep it at a fixed value so as to ensure the output of the exciter The amplitude of the three-phase alternating current reaches stability, and then provides enough stable excitation current for starting the main generator.

The control block diagram is shown in Figure 3.

(f ₁ -f _r ) ^* is the difference between the AC frequency applied to the stator of the given exciter and the frequency of the induced magnetic force of the motor rotor, where f ₁ =2π/ω ₁ , f _r =2π/ω _r =p·n/60 , p is the number of pole pairs of the main generator, and since the exciter is coaxially installed with the main generator, the rotor speed is the same.

In order to verify the feasibility and effectiveness of the control method of the present invention, Matlab8.1 is used for simulation verification.

Figure 4 is the constant slip two-phase excitation AC starting control model established in Matlab software, where the exciter module is a motor model packaged by Simulink according to the formula (6), and the output three-phase winding is connected to a resistive load through a rotating rectifier ( It is equivalent to the rotor winding of the main generator), and the output observation value I _f is the excitation current of the main generator. It is required that the average value of the excitation current I _f of the main generator is 8A during the motor starting process, and the fluctuation is not more than 7.5%. The AC input of the exciter can be known from the formula (1) as two-phase AC with a phase difference of 90°. Only the maximum value of the excitation voltage U _m and the frequency of the excitation voltage are given, and a two-phase AC voltage can be formed inside the exciter module .

The simulation implementation of a three-stage starter/generator two-phase excitation constant-slip AC starting control method is divided into the following steps:

1. The stator of the exciter is supplied with a two-phase alternating current with a maximum value U _m of 270V and an initial excitation frequency f ₁ of 8 Hz, as shown in Figure 5;

2. Under the action of the initial two-phase excitation voltage, the rotor of the exciter induces an alternating magnetic field and outputs three-phase alternating current;

3. After being rectified by the rotary rectifier, the excitation voltage U _f is output to the rotor winding of the main generator. In the model of Fig. 4, the rotor of the main generator is equivalent to an RL resistive load, and the voltage U _f generates an excitation current I _f on the rotor of the main generator;

4. The speed of the main generator increases under the action of the excitation current I _f of the main generator and the external three-phase AC voltage. The ideal speed rising curve is simulated and equivalent by the ramp function, and the limit is 3500r/min;

5. The main generator and the exciter are coaxially installed, and the rotor speed of the exciter is the same as that of the main generator rotor, then the frequency of the induced magnetic force of the exciter rotor is f _r = p n/60, p is the number of pole pairs of the main generator, p=3 in this embodiment;

6. The difference between f ₁ and f _r is subtracted, and the obtained difference f1-fr is used as the feedback value to compare with the slip reference (f ₁ -f _r ) ^* . After PI (in the simulation, P=20, I= 0.1) Obtain the exciter excitation voltage frequency f ₁ ' after calculation;

7. The speed of the main generator continues to rise accordingly, and the excitation voltage and current remain relatively constant during this process.

Figure 6 shows the simulation output waveform of the constant slip three-stage starter/generator starting control. From the simulation results, the difference between the frequency of the AC frequency applied to the stator of the exciter and the frequency of the induced magnetic force of the motor rotor can follow the given slip, and the excitation current is basically Keeping 8A constant, with an average fluctuation of 6.25%, the average excitation current can meet the starting requirements of the three-stage generator/generator, which proves the effectiveness of the invention.

Claims (2)

1. A control model of three-stage starting/generator two-phase excitation constant slip alternating current starting is characterized in that the control model of the three-stage starting/generator two-phase exciter is as follows:

wherein: u shape_a、U_b、U_cThe voltages of a phase winding, b phase winding and c phase winding of the rotor respectively, theta is the excitation angular velocity, theta is_rAs angular speed of the rotor, K_rIn order to be a voltage conversion factor,is the stator winding impedance angle;

theta-omega₁t，ω₁Is the angular frequency of the exciting voltage, and t is the running time of the exciter;

theta is described_r＝ω_rt，ω_rIs the rotor electrical angular velocity;

the above-mentionedR_sIs the internal resistance of the stator winding, L_mFor mutual inductance of stator and rotor windings, L_sFor self-inductance of the stator winding, U_mIs the maximum value of the excitation voltage;

the above-mentioned

2. A control method for realizing two-phase excitation constant slip ac starting of a three-stage starter/generator by using the control model of claim 1, characterized by comprising the following steps:

step 1: the initial exciting voltage frequency is f for the stator of the two-phase exciter₁Maximum AC voltage amplitude of U_mIn which the initial f is₁I.e. given (f) for slip₁-f_r)^*And f is not more than 4Hz₁≤10Hz；

Step 2: the rotation speed n of the main generator is obtained by a position sensor of the main generator, the main generator and the exciter are coaxially arranged, and the induced magnetic potential frequency of the exciter rotor is f_rP is the pole pair number of the main generator;

and step 3: will f is₁And f_rDifference subtraction is carried out to obtain a difference value f₁-f_rGiven as feedback quantity and slip (f)₁-f_r)^*Comparing, and performing PI calculation to obtain new exciter exciting voltage frequencyf₁'；

And 4, step 4: exciting voltage is introduced to the stator of the two-phase exciter with the frequency f₁', the maximum AC voltage amplitude is U_mRepeating the step 2-4, and finishing the control when the rotating speed of the main generator is increased to the rated rotating speed.